This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project is aimed at immune reconstitution of SIV infected macaques comparing autologous CD4+ T cells collected prior to versus post SIV infection and expanded in vitro using anti-CD3/anti-CD28 coated immunobeads. The data generated during the past year suggest that CD4+ T cells collected early post SIV infection either under the umbrella of PMPA chemotherapy or in the absence thereof show expansion and immune restorative function similar to pre SIV infection collected cells. However, the data unequivocally show that a marked diminution of viral loads is imperative before initiation of adoptive transfer of autologous CD4 T cells in order to induce potent control of SIV replication. Delineation of viral and immune correlates continues to be followed as well as trafficking and survival of these cells following adoptive transfer. Another main area of investigation was the characterization of the CD4+ T cells as they are being expanded and more importantly their behavior beyond the expansion phase at the time they are being reinfused to the animal. While the cells uniformly display a central memory phenotype and express all markers of regulatory T cells, these cells conform functionally more to an effector profile based on cytokine secretion and the expression of activation and homing markers. Furthermore, while CCR5 expression is restored following the expansion and these cells become again susceptible to SIV infection, the viral replication appears inefficient compared to the same aliquots of non-expanded CD4 T cells. This property was restricted to R5 tropic viruses and preliminary findings ascribe such "deficiency" to altered CCR5 mediated signaling via the associated Gai/cAMP pathway, while the Gaq pathway controlling chemokine signaling and chemotaxis did not appear affected. Additional investigations into this mechanism are ongoing.